The present invention relates to a power semiconductor module constituted in such a manner that a plurality of semiconductor chips and a control circuit for controlling the plurality of semiconductor chips are housed in the same case.
FIG. 1 shows the structure of a conventional power semiconductor module, wherein the reference numeral 1 denotes a metal base, and numeral 2 and 2 denote insulated wiring substrates, respectively. The insulated wiring substrates 2 are each formed in such a manner that, on the front and back surfaces of a ceramics substrate, conductive layers composed of a metal such as, e.g. Cu are formed. The insulated wiring substrates 2 are each is fixed onto the metal base 1 by soldering the conductive layer formed on the back surface thereof. On the conductive layer formed on the front surface of each of the insulated wiring substrates 2, a plurality of semiconductor chips 3 are fixed by soldering, respectively.
The metal base 1 is fixed to a resin case 4, and electrode pads on the semiconductor chips 3 and the conductive layers on the front surfaces of the respective insulated wiring substrate 2 are connected to electrodes 5 provided on the resin case 4 through bonding wires 6. Further, the electrodes 5 on the resin case 4 are led to external terminals 8 provided in the upper portion of the resin case, through wirings 7 composed of a metal such as Cu or the like and buried in the resin case 4.
Further, within the resin case 4, a plurality of support pillars 10 in each of which a pin (electrode) 9 is buried are provided in a state projecting from the bottom. By the plurality of support pillars 10, a controlling substrate 11 is supported, and, the pins 9 extend through predetermined patterns on the controlling substrate 11 and are soldered thereto, whereby the fixation and electrical connection of the controlling substrates 11 are effected. On the controlling substrate 11, various parts such as IC (integrated circuits) etc. are mounted, these parts being coupled to one another by wiring patterns (not shown) to form a control circuit; and, by this control circuit, signals for controlling the semiconductor chips 3 are generated. The signals generated by the control circuit constituted on the controlling substrate 11 are fed to the electrode pads on the semiconductor chips 3 via the wiring patterns (not shown) on the controlling substrate 11, the pins 9, the electrodes 5 and the bonding wires 6.
FIG. 2 is s plan view of the conventional power semiconductor module shown in FIG. 1, wherein the controlling substrate 11 is not shown. In this conventional case, the semiconductor chips mentioned above each constitute an IGBT (Insulated Gate Bipolar Transistor) formed in such a manner that, on the back surface of the chip, a collector electrode is formed, while on the front surface of the chip, a plurality of (four, in this embodiment) emitter electrode pads 4 and one gate electrode pad G are formed.
As shown, the gate electrode pad G on the front surface of each semiconductor chip 3 is connected to the electrode 5 on the resin case 4 through the bonding wire 6, and further, the electrode 5 is connected to the controlling substrate 11 through the pin 9.
In the case of the conventional power semiconductor module shown in FIG. 1 and FIG. 2, the circuit must be composed by connecting the bonding wires 6 to the electrodes 5 on the resin case, and, in case of feeding the respective semiconductor chips 3 with the control system signals generated on the controlling substrate 11, there must be provided a space for signal connection in the resin case 4 as in the case of a main signal. Due to this, there has arisen the problem that, when a plurality of semiconductor chips are used, the module as a whole is increased in size, thus resulting in an increase in the manufacturing costs.
As a result of the limitation on the connection with the resin case 4, a limitation is also placed on the disposition of the semiconductor chips 3; and thus, there has arisen the problem that the inductance component of the wirings is increased, thus resulting in the occurrence of the adverse effect that the reliability falls.
Here, as for the fact that the electrodes of the control signal system (gate control signal) are provided on the resin case disposed around the semiconductor chips, it is because the wire bonding connection steps can be continuously carried out as one step.
The reason why the module as a whole is large in size is that, as shown in FIG. 2, spaces for provision of the gate-relaying electrodes (electrodes 5) and the pins 9 need to be provided.
Further, as for the increase in the inductance component, the wiring length of the collector/emitter wirings plays a big role.